CN105070823A - Pressure sensor and manufacturing method thereof - Google Patents

Abstract

The invention belongs to the technical field of semiconductor sensors, in particular to a pressure sensor and a preparation method thereof. The pressure sensing device of the present invention includes at least one field effect transistor and a piezoelectric control gate; the field effect transistor is an NMOS transistor or a PMOS transistor; the piezoelectric control gate includes a piezoelectric film, an upper surface electrode of the piezoelectric film, An electrode on the lower surface of the piezoelectric film, and a connecting electrode between the gate of the field effect transistor and the electrode on the lower surface of the piezoelectric film. The pressure sensing device proposed by the present invention is used for sensing pressure signals, and has the characteristics of simple manufacturing process, small unit area, high chip integration, high sensitivity to pressure, and the like.

Description

A pressure sensor device and its manufacturing method

technical field

The invention belongs to the technical field of pressure sensors, and in particular relates to a highly integrated pressure sensor and a manufacturing method thereof, in particular to a pressure sensor combined with a piezoelectric film and a field effect transistor and a manufacturing method thereof.

Background technique

Pressure sensors are widely used in electronic products. Different application fields have different requirements for the structure, performance and density of pressure sensors. Some require higher resolution, such as electronic scales and barometers; High integration density, such as touch screen. In order to realize the perception of tiny external pressure signals, smart skin requires both higher resolution and higher integration density.

Traditional pressure sensors are divided into semiconductor piezoresistive pressure sensors and electrostatic capacitive pressure sensors. The former is to deform the sheet by external force to produce piezoresistance effect, so that the change of impedance is converted into an electrical signal; the latter is to convert the glass The fixed pole and the movable pole of the silicon face each other to form a capacitance, and the deformation of the movable pole by an external force causes a change in the electrostatic capacity, thereby converting it into an electrical signal. Due to the large size of a single device of a traditional pressure sensor, the integration level is very low.

Wang Zhonglin et al. used zinc oxide nanofibers to make piezoelectric pressure sensors[1], which greatly increased the integration density of the device, but due to the difficulty in controlling the uniformity of nanofiber clusters, the process of piezoelectric pressure sensors was very complicated and increased the number of devices. the cost of. Compared with growing uniform nanofibers, uniform film structures are easier to obtain. The invention combines the piezoelectric thin film with the field effect transistor technology, can manufacture a high-sensitivity pressure sensor, has high integration, and the technology is compatible with the existing field effect transistor technology.

[1] Wu, Wenzhuo, XiaonanWen, and ZhongLinWang.

Contents of the invention

The object of the present invention is to provide a pressure sensing device with small device unit area and high integration and its preparation method.

The invention combines the piezoelectric material with the traditional field effect transistor, and with the help of the mature field effect transistor preparation process, is suitable for the pressure sensor device, can greatly reduce the unit area of a single pressure sensor, and improve the integration degree of the device.

The pressure sensing device provided by the invention includes a field effect transistor and a piezoelectric control gate.

In the present invention, the field effect transistor is an NMOS transistor or a PMOS transistor.

In the present invention, the piezoelectric control grid includes: a piezoelectric film, an electrode on the upper surface of the piezoelectric film, an electrode on the lower surface of the piezoelectric film, and an electrode between the gate of the field effect transistor and the electrode on the lower surface of the piezoelectric film. connecting electrodes.

In the present invention, an insulating dielectric filler is further included between the field effect transistor and the piezoelectric control gate, and the insulating dielectric filler is formed of silicon dioxide, silicon nitride, silicon oxynitride or an insulating material with a low dielectric constant.

In the present invention, the piezoelectric film is formed of piezoelectric material; the upper surface electrode of the piezoelectric film is formed of metal, alloy or doped polysilicon; the lower surface electrode of the piezoelectric film is formed of metal, alloy or The doped polysilicon is formed; the connection electrode between the gate of the field effect transistor and the lower surface electrode of the piezoelectric film is formed by metal, alloy or doped polysilicon.

In the present invention, the piezoelectric material includes zinc oxide, piezoelectric ceramics, polyvinylidene fluoride and other piezoelectric polymers.

The present invention proposes a preparation method of the pressure sensor device, the specific steps are as follows:

Prepare field effect transistors and their source and drain interconnections according to standard processes, and form silicon wafers after chemical mechanical polishing;

Depositing a layer of insulating medium on the silicon wafer;

Depositing a hard mask layer on the surface of the insulating medium, and defining the position of the connection electrode between the gate of the field effect transistor and the lower surface electrode of the piezoelectric film through a photolithography process and an etching process;

Using the hard mask layer as a mask to etch to form a vertical via, the depth of etching needs to expose the gate electrode of the field effect transistor;

Etching away the remaining hard mask layer;

Depositing a conductor material in the formed vertical channel to form a connection electrode between the gate of the field effect transistor and the electrode on the lower surface of the piezoelectric film;

Chemical mechanical polishing is then performed on the structured surface to remove excess conductor material;

Then deposit conductive material on the surface of the formed structure to form the lower surface electrode of the piezoelectric film;

preparing a piezoelectric film on the lower surface electrode of the piezoelectric film;

Next, deposit conductive material on the piezoelectric film to form the upper surface electrode of the piezoelectric film.

In the method for preparing a pressure sensing device as described above, the conductor is formed of metal, alloy or doped polysilicon; the insulating medium is made of silicon dioxide, silicon nitride, silicon oxynitride or an insulating material with a low dielectric constant form.

In the method for preparing a pressure sensing device as described above, the connection electrode between the gate of the field effect transistor and the electrode on the lower surface of the piezoelectric film is in contact with the gate electrode of the field effect transistor, and is in contact with the piezoelectric film. The lower surface of the film is in electrode contact.

As for the method for preparing the pressure sensing device mentioned above, the method for preparing the piezoelectric film includes nanoimprinting, spin coating and other chemical growth methods.

In the pressure sensing device proposed by the present invention, the piezoelectric film will induce a voltage signal under the action of an external force, and the voltage generated by different external forces is different, and the induced voltage signal controls the gate of the field effect transistor, thereby controlling the gate of the field effect transistor. Output signal, according to the output signal of the field effect transistor, the existence and magnitude of pressure can be determined. The invention has the advantages of simple manufacturing process, small unit area, high chip integration, high sensitivity to pressure, and the like.

Description of drawings

FIG. 1 is a cross-sectional view of an embodiment of a pressure sensor proposed by the present invention.

Fig. 2 and Fig. 3 are respectively top views of two embodiments of the pressure sensor proposed by the present invention.

4-12 are process flow charts of an embodiment of the manufacturing method of the pressure sensor proposed by the present invention.

Fig. 13 and Fig. 14 are respectively a circuit diagram and an equivalent circuit diagram of an embodiment of the polarization of the polyvinylidene fluoride piezoelectric film proposed by the present invention.

Detailed ways

The present invention will be further described in detail below in conjunction with the accompanying drawings and specific embodiments. In the drawings, the thicknesses of layers and regions are exaggerated for convenience of illustration, and the shown sizes do not represent actual sizes. The referenced figures are schematic illustrations of idealized embodiments of the invention, and the illustrated embodiments of the invention should not be construed as limited to the particular shapes of regions illustrated in the figures but are to include resulting shapes, such as manufacturing-induced deviations. For example, the curves obtained by etching are usually curved or rounded, but in the embodiment of the present invention, they are all represented by rectangles. The representation in the figure is schematic, but this should not be considered as limiting the scope of the present invention.

Fig. 1 is an embodiment of the pressure sensor proposed by the present invention, which is a longitudinal sectional view of the device. As shown in Figure 1, the pressure sensor proposed by the present invention includes a field effect transistor composed of a substrate 101, a source 102, a drain 103, a gate oxide layer 104 and a gate 105, and an electrode 107 leads the source 102 out , the electrode 108 leads out the drain 103 , and the electrode 106 leads out the gate 105 . Among them, the field effect transistor can be NMOS or PMOS. Since the field effect transistor manufacturing technology is a relatively mature technology, the various parts are only drawn symbolically here. The electrodes 106 , 107 and 108 are made of metal, alloy or doped polysilicon; the insulating medium 109 is made of silicon dioxide, silicon nitride, silicon oxynitride or low dielectric constant insulating material.

The piezoelectric film 111 is the main piezoelectric conversion component, and the lower surface electrode 110 of the piezoelectric film and the upper surface electrode 112 of the piezoelectric film can ensure that the voltage induced by the piezoelectric film 111 acts on the gate 105 of the field effect transistor through the electrode 106 on, thereby controlling the field effect transistor. The piezoelectric film 111 is formed of zinc oxide, piezoelectric ceramics, polyvinylidene fluoride or other piezoelectric polymers, and the lower surface electrode 110 of the piezoelectric film and the upper surface electrode 112 of the piezoelectric film are made of metal, alloy or doped polysilicon form.

The insulating medium 301 plays the role of isolation, and the larger thickness of the insulating medium 301 can reduce the parasitic effect of the device and increase the resolution of the pressure sensor; the insulating medium 301 is made of silicon dioxide, silicon nitride, silicon oxynitride or low-dielectric Electrical constant insulating material is formed.

The piezoelectric film 111 is located vertically above the gate electrode 105 , and the effective area of the piezoelectric film 111 is larger than that of the gate electrode 105 in order to obtain a larger piezoelectric signal. Fig. 2, Fig. 3 are two embodiments of the top view of the piezoelectric sensor proposed by the present invention, the grid electrode 105 is located directly below the piezoelectric film 111, as shown in Fig. 2; in order to meet different design requirements, the grid electrode 105 is also It may be located under the side of the piezoelectric film 111 , as shown in FIG. 3 , the electrode 106 is connected to the lower surface electrode 110 of the piezoelectric film through a conductor interconnection line 201 . Conductor interconnection lines 201 are formed of metals, alloys, and doped polysilicon.

The piezoelectric sensor device disclosed in the present invention can be manufactured by many methods. The following describes the process flow of an embodiment of the present invention for manufacturing the piezoelectric sensor device with the structure shown in FIG. 1 .

First, as shown in FIG. 4 , it is a field effect transistor with complete functions, and the drain interconnection electrode 107 and the source interconnection electrode 108 have been prepared. The field effect transistor manufacturing process is already a relatively mature technology. Here, the various parts of the field effect transistor are only symbolically drawn. The top view of the device corresponding to the device structure in Fig. 4 is shown in Fig. 5, and the electrodes are separated by an insulating medium 109 for electrical isolation.

Next, deposit an insulating medium 301 on the surface of the field effect transistor, then spin-coat photoresist 302 on the surface of the insulating medium 301, and dry it, as shown in Figure 6; at this time, the top view of the device corresponding to the device structure is shown in Figure 7 As shown, in order to concisely show the relative positions of the insulating medium 301 and the field effect transistor, here the source 102, the drain 103 and the gate electrode 105 of the field effect transistor are drawn with dotted lines.

Next, the position of the electrode 106 is photoetched, as shown in FIG. 8 , the insulating medium 301 and the insulating medium 109 are etched to expose the surface of the gate electrode 105 , so as to ensure good contact between the gate electrode 105 and the electrode 106 . The top view of the device corresponding to the device structure at this time is shown in FIG. 9 , and the gate electrode 105 can be clearly seen from FIG. 9 .

Then the photoresist 302 is etched away, the conductor material is deposited to obtain the electrode 106, and a flat surface is obtained by chemical mechanical polishing to facilitate subsequent processes, as shown in FIG. 10 . A top view of the device corresponding to the device structure at this time is shown in FIG. 11 .

Next, deposit the conductive material to obtain the lower surface electrode 110 of the piezoelectric film, and make a uniform piezoelectric film 111 on the lower surface electrode 110 of the piezoelectric film by nanoimprinting, spin coating or other chemical growth methods, and then deposit The conductive material forms the upper surface electrode 112 of the piezoelectric film, and the basic structure of the pressure sensor is completed. As shown in Figure 12.

For different piezoelectric materials, a uniform piezoelectric film can be obtained by different preparation methods, for example, a film of polyvinylidene fluoride can be obtained by spin-coating an organic solution of polyvinylidene fluoride on the bottom electrode 110 of the piezoelectric film, Then the film is dried to form a polyvinylidene fluoride film. Since polyvinylidene fluoride has an obvious piezoelectric effect after polarization, after the basic structure of the pressure sensor is completed, the substrate 101 of the field effect transistor and the piezoelectric A DC voltage source 401 is applied to the upper electrode 112 of the film to polarize the polyvinylidene fluoride piezoelectric film 111 , as shown in FIG. 13 .

Figure 14 shows the equivalent circuit diagram of the polarized circuit of the polyvinylidene fluoride piezoelectric film. Since only the gate oxide layer 104 and the piezoelectric film 111 are insulating media in the circuit, the polarization of the polyvinylidene fluoride piezoelectric film can be The circuit is regarded as a series connection of a DC voltage source 401, a piezoelectric film capacitor 402, and a gate oxide layer capacitor 403. Under the condition that the gate oxide layer 104 is not broken down, the polarity of the polyvinylidene fluoride piezoelectric film 111 can be achieved. change.

As mentioned above, many widely different embodiments can be constructed without departing from the spirit and scope of the present invention. It should be understood that the invention is not limited to the specific examples described in the specification, except as defined in the appended claims.

Claims (8)

1. a pressure sensor, is characterized in that, comprises a field-effect transistor and a piezoelectricity control gate; Wherein:

Described field-effect transistor is nmos pass transistor or PMOS transistor;

Described piezoelectricity control gate comprises piezoelectric membrane, the upper surface electrode of piezoelectric membrane, the lower surface electrode of piezoelectric membrane, the connecting electrode between described field effect transistor gate and the lower surface electrode of piezoelectric membrane.

2. pressure sensor according to claim 1, it is characterized in that, comprise dielectric filler between described field-effect transistor and piezoelectricity control gate, this dielectric filler is formed by the insulating material of silicon dioxide, silicon nitride, silicon oxynitride or low-k.

3. pressure sensor according to claim 1, is characterized in that, described piezoelectric membrane is formed by piezoelectric; The upper surface electrode of described piezoelectric membrane is formed by the polysilicon of metal, alloy or doping; The lower surface electrode of described piezoelectric membrane is formed by the polysilicon of metal, alloy or doping; Described connecting electrode between field effect transistor gate and the lower surface electrode of piezoelectric membrane is formed by the polysilicon of metal, alloy or doping.

4. pressure sensor according to claim 3, is characterized in that, described piezoelectric, is selected from zinc oxide, piezoelectric ceramic, Kynoar and other piezopolymers.

5. the preparation method of pressure sensor as claimed in claim 1, it is characterized in that, concrete steps are as follows:

Prepare the interconnection line of field-effect transistor and source electrode and drain electrode, after chemico-mechanical polishing, form silicon wafer;

Deposit one deck dielectric on described silicon wafer;

At described dielectric surface deposition one hard mask layer, and defined the position of the connecting electrode between described field effect transistor gate and the lower surface electrode of piezoelectric membrane by photoetching process and etching technics;

With described hard mask layer for mask etching forms vertical passage, the degree of depth of etching need expose the gate electrode of described field-effect transistor;

Etch away remaining hard mask layer;

Conductor deposited material in established vertical channel, forms the connecting electrode between described field effect transistor gate and the lower surface electrode of piezoelectric membrane;

Then chemico-mechanical polishing is carried out to the surface forming structure, remove unnecessary conductor material;

Then the lower surface electrode of piezoelectric membrane is formed at the surface deposition conductor material forming structure;

The lower surface electrode of described piezoelectric membrane prepares piezoelectric membrane;

Then, on described piezoelectric membrane, conductor deposited material forms the upper surface electrode of piezoelectric membrane.

6. the preparation method of pressure sensor according to claim 5, is characterized in that, described conductor is formed by the polysilicon of metal, alloy or doping; Described dielectric is formed by the insulating material of silicon dioxide, silicon nitride, silicon oxynitride or low-k.

7. the preparation method of pressure sensor according to claim 5, it is characterized in that, described connecting electrode between described field effect transistor gate and the lower surface electrode of piezoelectric membrane contacts with the gate electrode of described field-effect transistor, and contacts with the lower surface electrode of described piezoelectric membrane.

8. the preparation method of pressure sensor according to claim 5, is characterized in that, the preparation method of described piezoelectric membrane is nano impression, spin coating or chemically grown method.